add blank=True to fields of Vulnerability and Package (#433)

add `blank=True` to Vulnerability.old_vulnerability_id and Package.qualifiers

Signed-off-by: 司芳源 <sify1221@gmail.com>

Author: sify21

vulnerabilities/models.py

@@ -54,6 +54,7 @@ class Vulnerability(models.Model):
         help_text="empty if no  CVE else VC id",
         unique=True,
         null=True,
+        blank=True,
     )
     summary = models.TextField(
         help_text="Summary of the vulnerability",
@@ -162,6 +163,7 @@ class Meta:
             "Extra qualifying data for a package such as the name of an OS, "
             "architecture, distro, etc."
         ),
+        blank=True,
         null=False,
     )